As a technology for transmitting a video data item or an audio data item, a millimeter-wave wireless technology using a 60-GHz band, which can utilize a broad bandwidth and which can realize high-speed wireless transmission, has drawn attention. A millimeter wave has properties that are similar to those of light, and has a high rectilinear-propagation property. In millimeter-wave wireless communication, because of the characteristics of a millimeter wave, communication is easily interrupted when a shielding object such as a human crosses a communication path.
In a WirelessHD specification that is a standard specification of the millimeter-wave communication technology, an HRP (High Rate PHY) that is a high-rate transmission channel and an LRP (Low Rate PHY) that is a low-rate transmission channel are defined. Regarding the HRP, an antenna having narrow directivity is used. Accordingly, the direction of arrival of a millimeter wave associated with communication paths is limited, but a high gain can be obtained. The HRP is used to transmit a data item, such as an uncompressed video data item, at a high rate. On the other hand, regarding the LRP, the rate is low, and an antenna having wide directivity is used. Accordingly, when the LRP is compared with the HRP, the direction of arrival of a millimeter wave associated with communication paths is not limited, and a communication path is not easily interrupted. The LRP is used to transmit a compressed video data item, a control data item, and so forth. Furthermore, in WirelessHD, when interruption of a communication path is detected, a scheme is employed, in which switching to another communication path is performed by utilizing reflection of a millimeter wave at a wall or the like, and in which communication is restored.
As described above, in WirelessHD, proper use of the HRP and the LRP is realized by selecting either one of the channels, namely, the HRP and the LRP. Furthermore, when interruption of a communication path is detected, switching among communication paths is performed. In this manner, WirelessHD copes with the above-described problem of a millimeter wave.